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September 2021 – Current Transformers

Published on: 14/09/2021

Getting to know current transformers by GD Rectifiers

Sirio Current Transformers by GD Rectifiers.

Current transformers, also known as CT’s are instruments used to transform the current from a high current into a lower current enabling the power to be used for measuring and controlling.

A current transformer consists of a core and a primary and secondary winding. GD Rectifiers offers a wide range of reliable current transformers in various current ratings, transformer types, supply voltages and mounting types. GD Rectifiers’ extensive range of current transformers are supplied by Telcon and Sirio Inductive Components.


How does a current transformer work?

Current transformers are also known as “step down transformers”, the primary winding, a magnetic flux is created when an alternating current flows through, which induces an alternating current in the secondary winding. A current transformers alternating current is proportionate to the current in its primary, and once the current has been reduced it can be safely measured by using an ammeter.


Types of current transformers

Toroidal Current Transformer – these current transformers do not contain primary winding and are shaped like a doughnut. The line that carries the current flowing in the network is threaded through a window or hole in the toroidal transformer. The benefits of using a toroidal current transformer is that they offer high efficiency with minimal excess noise and little to no excess leakage inductance.

Wound Current Transformers – the primary winding of these wound current transformers is physically connected in series with the conductor that the carries the measured current flowing in the circuit. The scale of the secondary current is dependent on the turns ratio of the transformer.

Bar-type Current Transformer – this type of current transformer uses the cable or busbar of the main circuit as the primary winding, the equivalent to a single turn. Bar-type current transformers are fully insulated from the high operating voltage of the system and are usually bolted to the current carrying device.


Typical Applications

Current transformers are used in a wide range of industrial and commercial measurement applications. Some of the most common include: generating stations, electrical substations, commercial electric power distribution and Electrical panels.


GD Rectifiers offers a large range of current transformers from Sirio Inductive Components including: main frequency current transformers, current transformers for measurement applications, current transformers for high frequency applications, EE core based drive transformers, low coupling capacity gate drive transformers and ring core based gate drive transformers.


GD Rectifiers also distributed Telcon’s current and voltage transformers, a range of panel mounted units from 25A-500A and consist of the coil and Hall element only, where the user included the active circuitry on their PCB. All units are designed for primary current cable and are available for vertical mounting up to 100A and horizontal mounting from 25A-500A.

Telcon Current and Voltage Transformers by GD Rectifiers

For further information on current transformers, or to discuss your enquiry, please call GD Rectifiers on: 01444 243 452 or email:

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